U.S. patent number 4,636,808 [Application Number 06/773,497] was granted by the patent office on 1987-01-13 for continuous ink jet printer.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to Denver A. Herron.
United States Patent |
4,636,808 |
Herron |
January 13, 1987 |
Continuous ink jet printer
Abstract
In an ink jet print head for a continuous type ink jet printer,
both drop charging and drop deflection are achieved by a single,
nonextended, planar electrode disposed adjacent the drop separation
point of the ink jet filament, eliminating the need for separate
drop deflection electrodes or extended drop charging electrodes for
achieving drop deflection, and simplifying the construction of the
ink jet print head.
Inventors: |
Herron; Denver A. (Dayton,
OH) |
Assignee: |
Eastman Kodak Company
(Rochester, NY)
|
Family
ID: |
25098481 |
Appl.
No.: |
06/773,497 |
Filed: |
September 9, 1985 |
Current U.S.
Class: |
347/76;
347/77 |
Current CPC
Class: |
B41J
2/09 (20130101); B41J 2/085 (20130101) |
Current International
Class: |
B41J
2/085 (20060101); B41J 2/09 (20060101); B41J
2/075 (20060101); G01D 015/18 () |
Field of
Search: |
;346/1.1,75 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goldberg; E. A.
Assistant Examiner: Preston; Gerald E.
Attorney, Agent or Firm: Close; Thomas H.
Claims
I claim:
1. A print head for a continuous ink jet printer, of the type
having planar electrode drop charging means disposed adjacent the
drop separation point of an ink jet filament and a drop catcher
having a vertical drop catching face extending generally parallel
to the ink jet filament, and means for deflecting charged ink drops
into said drop catching face, characterized by said drop charging
means and drop deflection means comprising a single, nonextended,
planar electrode positioned near the drop separation point of the
ink jet filament, nonextended meaning that the planar electrode
does not extend onto said drop catching face.
2. The ink jet print head claimed in claim 1, wherein the drop
charging and deflecting electrodes are between 1 and 6 drop
spacings long.
3. The ink jet print head claimed in claim 1, wherein the drop
catcher comprises molded plastic material.
4. A print head for a continuous multijet ink jet printer,
comprising:
means for forming a plurality of ink jets arranged in a line, each
ink jet defining an ink filament separating into drops at a drop
separation point;
a corresponding plurality of planar electrodes located adjacent the
drop separation points of the respective ink jet filaments for
charging and deflecting ink drops;
a drop catcher having a vertical drop catching face extending
generally parallel with the ink jet filaments, said drop catching
face being located below said planar electrodes; and
an ink gutter located at the bottom of said drop catching face,
whereby ink drops deflected onto said drop catching face by said
planar electrodes flow down said face into said gutter.
Description
TECHNICAL FIELD
The present invention relates to a print head for a continuous ink
jet printer, and more particularly, to means for charging and
deflecting ink drops in such a print head.
BACKGROUND ART
In a continuous type (as distinguished from drop on demand type)
ink jet printer, conductive ink is forced through an orifice to
form an ink filament. The ink is vibrated at a constant frequency
to cause drops to regularly separate from the end of the filament.
A drop charging electrode located in the vicinity of the drop
separation point is employed to selectively induce an electric
charge on the conductive ink filament at the instant of drop
separation. The separating drop captures the electric charge
induced on the filament, and the charged drop is electrostatically
deflected, for example to a drop catcher.
In a continuous binary type ink jet printer, all charged drops are
deflected along a catch trajectory to a drop catcher, and uncharged
drops proceed along a print trajectory to a print receiving surface
such as paper.
In another type of ink jet printer, various amounts of charge are
selectively placed on the drops to deflect the drops along
respective print trajectories, or along a catch trajectory.
The print head of a prior art continuous ink jet printer generally
includes a reservoir for delivering the conductive ink, under
pressure, to an ink jet orifice; means for vibrating the ink, such
as a piezoelectric transducer attached to the reservoir; a charging
electrode for selectively charging the ink drops as they separate
from the filament; means for deflecting the charged drops; and
means for catching nonprinting drops.
In many prior art ink jet printing heads for continuous ink jet
printing, the charging electrode is a small cylindrical conductor,
generally formed by plating the inside of a microscopic hole in an
insulating sheet of material. The means provided for deflecting the
charged ink drops generally comprises a pair of deflection
electrodes, arranged like the plates of an air capacitor, to which
a constant deflection voltage is applied to establish an
electrostatic deflection field between the plates. The ink drops
travel between the plates, and the charged drops are deflected by
the electric field.
U.S. Pat. No. 3,656,171, issued Apr. 11, 1972 to J. A. Robertson,
discloses an ink jet printing head for continuous ink jet printing,
wherein the drop charging electrode is simply a plate disposed
adjacent the ink jet filament in the vicinity of drop separation,
and the means for deflecting the ink drops is simplified to an
electrically conductive surface that is arranged along one side of
the path of the ink drops. The construction of such an ink jet
printing head was substantially simpler than the prior art ink jet
print heads.
The theory proposed by Robertson regarding the operation of the
deflection means was that the charged ink drops induced a mirror
charge in the conductive surface. The charged drops were then
attracted to their mirror images, thereby causing the deflection.
This arrangement had the advantage of simplifying the construction
of the ink jet printing head by eliminating one half of the
previously required deflection electrode structure, and eliminating
the need for a separate high voltage power supply to charge the
deflection electrodes in the ink jet printer apparatus.
It was further noted by Robertson that the deflection means may
comprise an extension of the charging electrode, thereby further
simplifying the construction of the ink jet print head.
Such an arrangement is shown in FIG. 3, where an ink jet printing
head 10 includes an ink reservoir 12 containing conductive ink 14
under pressure. The ink is forced from an an orifice 16 to form an
ink filament 18. The ink is vibrated by means not shown, to cause
ink drops 20 to regularly separate from the ink filament 18. The
ink drops 20 are selectively charged by a voltage V.sub.C applied
to an extended drop charging electrode 22 from a charging circuit
24. Charged drops are deflected into a drop catcher 26, and
uncharged drops proceed to the printing surface 28.
Although this approach has the advantage of eliminating all
together the need for a separate deflection electrode, the extended
charging electrode protrudes into the region where deflected drops
may impact on the vertical face of the drop catcher. This is
undesirable, since the conductive ink stream may then ground the
charging electrode to the ink supply, or in the case of a multi-jet
print head, short adjacent charging electrodes. It is the object of
the present invention therefore to provide a simplified ink jet
printing head of the type having a simple planar drop charging
electrode located adjacent an ink jet filament in the region of the
drop separation, that is free from the shortcomings noted
above.
DISCLOSURE OF THE INVENTION
The object of the invention is achieved by eliminating any separate
means for drop deflection from the ink jet print head. The inventor
has determined that adequate deflection of charged drops is
achieved by the nearly instantaneous interaction between the drop
and the planar drop charging electrode alone, without the need for
separate drop deflection electrodes, or extended drop charging
electrodes to cause drop deflection. The continuous ink jet
printing head according to the present invention charges and
deflects ink drops into a vertical catcher face with a single,
nonextended, planar electrode located above the drop catcher face.
The term `nonextended` means that the drop charging electrode does
not extend onto the drop catching face.
According to a preferred mode of practicing the invention, the
planar nonextended drop charging electrode is between 1 and 6 drop
spacings long. The ink drop catcher is comprised of a molded
plastic material.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of an ink jet print head according to
the present invention;
FIG. 2 is a plan view of the drop charging electrode structure in a
multi-jet ink jet print head according to the present
invention;
FIG. 3 is a schematic diagram of a prior art ink jet printing head
having an extended drop charging electrode for ink drop deflection;
and
FIG. 4 is a perspective view of an electrode plate having
nonextended drop charging electrodes according to the present
invention.
MODES OF CARRYING OUT THE INVENTION
FIG. 1 shows an ink jet printing head 10 having a planar
nonextended drop charging electrode according to the present
invention, where elements similar to elements in the prior art
printing head shown in FIG. 3 are similarly numbered.
Printing head 10 includes an ink reservoir 12 containing conductive
ink 14 under pressure. The ink is forced from an orifice 16 to form
an ink filament 18. The ink is vibrated by means not shown to cause
the ink jet filament to reliably break up into drops 20. The ink
drops are selectively charged by voltage V.sub.C applied to a
nonextended planar drop charging electrode 22 from a charging
circuit 24. Charged drops are deflecting by nearly instantaneous
interaction with the nonextended planar drop charging electrode 22
onto the face of a drop catcher 26, and uncharged drops proceed to
the printing surface 28. No means other than the nonextended planar
drop charging electrode 22 is provided for causing the drops to
deflect onto the face of drop catcher 26. A preferred range of
lengths for the drop charging electrode 22 for use in the present
invention is between 1 and 6 drop spacings long a `drop spacing` is
the distance d between centers of two consecutive drops in the ink
jet (see FIG. 1).
According to a presently preferred mode of practicing the
invention, the ink jet print head produces 64 ink jets from a line
of orifices 31 .mu.m in diameter, and spaced on 84.6 .mu.m centers.
The ink jets are stimulated in syncronism at 75.1 kz. The
nonextended planar drop charging electrodes are carried by a charge
plate 30. An end view of the charge plate 30 showing the planar
nonextended drop charging electrodes 22 is shown in FIG. 2. Each
electrode 22 is 50.8 .mu.m wide and 965 .mu.m long and spaced on
84.6 .mu.m centers. For the ink jet filament produced and
stimulated as described above, this length of electrode corresponds
to approximately 6 drop spacings. It has been found through
experiment that an electrode having a length of as little as 1 drop
can be used to reliably deflect charged drops.
FIG. 4 is a perspective view of the charge plate 30, showing the
planar nonextended drop charging electrodes 22 and electrical
conductors 32 for electrically addressing the electrodes.
Referring to FIG. 1, in the preferred mode of practicing the
invention, the drop catcher 26 is formed from molded plastic
thereby reducing the cost of manufacture. Since all necessary drop
deflection is performed by the planar nonextended drop deflection
electrodes 22, there is no need for the drop catcher to be made
from electrically conductive material, or to include thereon the
electrically conductive electrode for drop deflection.
Although the preferred mode of practicing the invention has been
described with reference to an ink jet print head for a continuous
binary type ink jet printer, the principle of the present invention
can also be applied to the type ink jet printer where the drops are
deflected along several printing trajectories.
INDUSTRIAL APPLICABILITY AND ADVANTAGES
The ink jet printing head according to the present invention is
useful in continuous ink jet printing apparatus. The ink jet
printing head is advantageous in that by eliminating the need for
separate drop deflecting means, the construction of the ink jet
printing head is simplified, thereby reducing its manufacturing
cost. Since the drop catcher in the ink jet printing head does not
need to be conductive, or include a conductive electrode, it may be
simply constructed of molded plastic.
The invention has been described in detail with reference to a
particular embodiment, however, it will be understood that
variations and modifications can be made within the spirit and
scope of the invention as defined by the accompanying claims.
* * * * *